drm: fourcc: Add drm_format_plane_width_bytes()

drm: fourcc: Add drm_format_plane_width_bytes()

drm_format_plane_width_bytes() calculates and returns the number of bytes
for given width of specified format. The calculation uses @cpp
in drm format info for byte-aligned formats. If the format isn't
byte-aligned, @cpp should 0, and the macro pixel information is used.
This avoids bit level rounding.

Use this drm_fb_cma_get_gem_addr() for offset calculation.

Signed-off-by: Hyun Kwon <hyun.kwon@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>